Methods and compositions are provided that relate to the administration of a toxic agent to a subject in a formulation in which toxicity is substantially reduced.
Many therapeutic agents typified by chemotherapeutics are effective at treating a particular condition, but may at the same time have toxic side effects for the patients that significantly impact the quality of life for the patient. These toxic side effects may arise through the biological action of the agents. For example, a majority of chemotherapy agents kill cancer cells by acting on cells that are actively dividing and replicating. These agents unfortunately do not discriminate between cancer cells and actively dividing normal cells such as blood cells forming bone marrow, cells in the digestive tract, hair follicles, and reproductive cells. Because the chemotherapeutic agents are toxic, the effectiveness of the drug is limited because dosage levels and treatment frequency cannot exceed tolerance levels for non-cancerous cells. Moreover, the chemotherapy regimen often dramatically diminishes the quality of a patient""s life through its physical and emotional side effects.
In attempts to overcome the problems of toxicity, chemotherapeutic agents have been targeted to tumor cells by covalently binding the agent to a carrier macromolecule that binds a specific receptor on the surface of a target cell. The carrier molecule is commonly a protein or glycoprotein but may also be a carbohydrate. Limitations of this approach include the ability of the conjugate to effectively and selectively bind the drug target.
An alternative approach to treating patients is to search for therapeutic agents that act on targets that are only associated with diseased tissue. For example, certain cancer drugs are being developed that inhibit angiogenesis, an activity that is essential for growth of a tumor but not otherwise essential in an adult subject except for wound healing or during the menstrual cycle. Another approach is to inhibit tumor metastasis. Potential anti-metastatic agents include a class of modified citrus pectins which are polysaccharides that prevent metastasis of primary tumors by acting as antagonists for growth factors that interact with cell receptors to prevent metastasized cells from lodging at a secondary site (Platt et al. J. Natl Cancer Inst. 84, 438-442 (1992); U.S. Pat. No. 5,801,002, Raz, U.S. Pat. No. 5,895,784). Carbohydrate binding proteins have also been used to prevent metastasis of tumors. These compounds are galactose specific carbohydrate binding proteins that bind to galactose binding sites on metastatic cells and interfere with cell-cell interactions necessary during metastasis. (Platt: U.S. Pat. No. 5, 681,923). Simple sugars such as methyl-xcex1-D lactoside and lacto-N-tetrose have been shown to inhibit metastasis of B 16 melanoma cells, while D-galactose and arabinogalactose inhibited liver metastasis of L-1 sarcoma cells (Beuth et al. J. Cancer Res. Clin. Oncol. 113, 51, 1987).
Despite the increasing resources applied to develop new therapies for cancer, survival rates for most cancer patients have not materially improved over the last 15 years (American Cancer Society, 1995 xe2x80x9cCancer Facts and Figuresxe2x80x9d). In most cases, particularly when a tumor is not detected at an early stage, cancer chemotherapy merely partially prolongs a patient""s life, often for only a few months. Given the rigors of repeated chemotherapeutic treatments, and taking into account the low response rates and the modest effects on survival time, significant toxicity and side effects which reduce the patient""s quality of life have become a major issue. Increasing efficacy of a drug can be translated into decreasing of the dosage of the drug, and decreasing its toxicity. Further, decreasing of toxicity per se leads to improvement of the patient""s quality of life.
However effective a therapeutic agent may be in modifying an abnormal biological condition, undesirable toxic side-effects impinge on the optimum use of the agents.
In an embodiment of the invention, a method is provided for delivering an effective dose of a therapeutic agent to a subject in a formulation that reduces the toxic side effects of the agent that includes the step of providing a polysaccharide, for example a galactomannan, combining the polysaccharide with the effective dose of the agent to form a mixture; and administering the mixture to the subject. The agent may be a chemotherapeutic agent. Moreover, the mixture may be administered parenterally.
In a further embodiment, a method is provided for treating a cancer in a subject, comprising: administering parenterally an effective dose of a chemotherapeutic agent in a mixture with an effective dose of a galactomannan.
An example of a galactomannan is a polysaccharide having a size is in the range of 20,000-600,000 D or in the range of 90,000 to 415,000 D or in the range of 40,000-200,000 D. In specific examples, the galactomannan may have an average size of 83,000D or 215,000D. In a further embodiment of the invention, the galactomannan is isolated from an isolate from Gleditsia triacanthos. In a further embodiment, a hydrolysis product of the gcalactomannan is obtained which is has a lower molecular weight than the isolated non-modified form. In other embodiments of the invention, a galactomannan is obtained which is a derivative of an isolate from Medicago falcata. 
In embodiments of the invention, a galactomannan is used to reduce toxicity of a therapeutic agent when it is mixed with the agent prior to administration. The galactomannan may be a xcex21,4 D-galactomannan. Moreover, the galactomannan may include a ratio of 2.0-3.0 mannose to 0.5-1.5 galactose. The ratio of mannose to galactose may be 2.6 mannose to 1.5 galactose or 2.2 mannose to 0.9 galactose or 1.13 mannan to 1 galactose or 2.2 mannose to 1 galactose.
The ratio of galactomannan to chemotherapeutic agent in the mixture may be in the range of 0.1:1 w/w to 10:1 w/w. In an embodiment of the invention, the mixture has a reduced toxicity of greater than 50% compared with the same dose of the agent absent galactomannan. The mixture may have a reduced toxicity of greater than 80% compared with the same dose of the agent absent galactomannan.
In an embodiment of the invention, the therapeutic agent is a chemotherapeutic agent, for example, adriamycin or 5-Fluorouracil (5-FU).
A further embodiment of the invention provides a method for use in treating a cancer including any of chronic leukemia, breast cancer, sarcoma, ovarian carcinoma, rectal cancer, throat cancer, melanoma, colon cancer, bladder cancer, lung cancer, mammary adenocarcinoma, gastrointestinal cancer, stomach cancer, prostate cancer, pancreatic cancer, or Kaposi""s sarcoma.
In an embodiment of the invention, a cancer therapeutic formulation with reduced toxicity includes an effective dose of a galactomannan, and an effective dose of a chemotherapeutic agent in a mixture. The formulation may further include a cancer therapeutic in which the formulation is in a powder form or in a liquid form.
The following terms shall have the meanings indicated herein and in the claims, unless required otherwise by the context.
The term xe2x80x9csubjectxe2x80x9d is defined here and in the claims as a mammal including a human in need of therapy for, or susceptible to, a condition or its sequelae. The subject may include dogs, cats, pigs, cows, sheep, goats, horses, rats, and mice and humans. The term xe2x80x9csubjectxe2x80x9d does not exclude an individual that is normal in all respects.
The term xe2x80x9cpatientxe2x80x9d shall mean a human subject who has presented at a clinical setting with a particular symptom or symptoms suggesting the need for treatment.
The term xe2x80x9cpolysaccharidexe2x80x9d refers to polymers comprised primarily of monomers of one or more sugars and substituted sugars. When isolated from nature, polysaccharide preparations comprise molecules that are heterogeneous in molecular weight.
xe2x80x9cEfficacyxe2x80x9d of a therapeutic agent refers to the relationship between a minimum effective dose and an extent of toxic side effects. Efficacy of an agent is increased if a therapeutic end point can be achieved by administration of a lower dose or a shorter dosage regimen. If toxicity can be decreased, a therapeutic agent can be administered on a longer dosage regimen or even chronically with greater patient compliance and improved quality of life. Further, decreased toxicity of an agent enables the practitioner to increase the dosage to achieve the therapeutic endpoint sooner, or to achieve a higher therapeutic endpoint.
The term xe2x80x9cpharmaceutically acceptable carrierxe2x80x9d refers to any and all solvents, dispersion media, e.g., human albumin or cross-linked gelatin polypeptides, coatings, antibacterial and antifungal agents, isotonic, e.g., sodium chloride or sodium glutamate, and absorption delaying agents, and the like that are physiologically compatible. The use of such media and agents for pharmaceutically active substances is well known in the art. Preferably, the carrier is suitable for oral, intravenous, intramuscular, subcutaneous, parenteral, spinal or epidural administration (e.g., by injection or infusion). Depending on the route of administration, the active compound can be coated in a material to protect the compound from the action of acids and other natural conditions that can inactivate the compound. xe2x80x9cParenteral administrationxe2x80x9d includes but is not limited to administration by bolus injection or infusion, as well as administration by intravenous, intramuscular, intraarterial, intrathecal, intracapsular, intraorbital, intracardiac, intradermal, intraperitoneal, transtracheal, subcutaneous, subcuticular, intraarticular, subcapsular, subarachnoid, intraspinal, epidural and intrasternal injection and infusion.
The term xe2x80x9ctoxicxe2x80x9d as used herein means any adverse effect caused by an agent when administered to a subject.
We provide a method of treating a subject with a therapeutic agent that minimizes the toxic side effects of the therapeutic agent. The method requires the co-administration of the agent with a polysaccharide. In addition to reducing toxicity, the co-administration of a polysaccharide with a therapeutic agent may increase the efficacy of the agent. In embodiments of the invention, the polysaccharide, galactomannan, has been shown to be effective in reducing the toxic side effects of therapeutic agents when coadministered with the agents. Although the examples provided herein describe the beneficial effects of galactomannans, we do not exclude the possibility that other polysaccharides may have a similar effect. The observed reduction in toxicity of a toxic therapeutic agent makes it possible to administer a greater dose without an increase in adverse side effects associated with treatment. The administration of increased dosages of a therapeutic agent having toxic side effects may be beneficial for treatment of a number of diseases including cancer, where the toxic side effects of traditional cytotoxic agents have limited their use.
In addition to reducing toxicity, efficacy may be enhanced by administering a therapeutic agent with a galactomannan. The increase in efficacy may arise from a synergistic effect between the galactomannan and the therapeutic agent mixture.
Both the polysaccharide and the agent may separately be formulated, in a dry form for example as a powder, or in a liquid form. In a preferred embodiment, the polysaccharide and therapeutic agent are mixed prior to administration. The mixture may be in the form of a liquid, a powder or an aerosol.
The dosage regimens for established therapeutic agents with known toxic side effects has been established and are described in the Physician""s Desk Reference. For example, a description of adriamycin can be found in the Physician""s Desk Reference 48th Edition (1994) pp 459-461 and for 5-FU on pages 1924-1925, these descriptions being incorporated by reference. The co-administration of polysaccharide with a therapeutic agent may utilize but is not limited to the dosage regimen and route of administration already established and approved for the therapeutic agent, the difference being the inclusion of the polysaccharide. For example, a single bolus can be administered, several divided doses can be administered over a period of time, or a dose can be proportionally reduced and administered over a time period by infusion, or can be increased, as indicated by the exigencies of the therapeutic situation. The dosage unit will be a mixture of polysaccharide with therapeutic agent. However we do not exclude the possibility that the polysaccharide and therapeutic agent could be administered sequentially as distinct formulations.
The formulation of the mixture may be derived from the standard formulation of the therapeutic agent to which the polysaccharide is added in a compatible solvent or as a powder. For example, the chemotherapeutic agent 5-FU is commonly formulated in an aqueous solution with excipients. In Example 1, aqueous galactomannan was added to the aqueous 5-FU to provide the formulation that was administered to the subject.
Pharmaceutically acceptable carriers are commonly added in typical drug formulations. For example in oral formulations, hydroxypropyl cellulose, colloidal silicon dioxide, magnesium carbonate, methacrylic acid copolymer, starch, talc, sugar sphere, sucrose, polyethylene glycol, polysorbate 80, and titanium dioxide: croscarmellose sodium, edible inks, gelatin, lactose monohydrate, magnesium stearate, povidone, sodium lauryl sulfate, carnuba wax, crospovidone, hydroxypropyl methylcellulose, lactose, microcrystalline cellulose, and other ingredients may be used. In addition, galactomannan has been used as a carrier for oral delivery of agents which are in a non-liquid form. (U.S. Pat. Nos. 4,447,337; 5,128,143; and 6,063,402).
One of ordinary skill in the art can determine and prescribe the effective amount of the therapeutic composition required based on clinical protocols. In general, a suitable daily dose of a composition of the invention will be that amount of the composition, which is the lowest dose effective to produce a therapeutic effect.
Embodiments of the invention demonstrate that administration of a mixture of a polysaccharide and a toxic therapeutic may result in reduced toxicity. An example of a polysaccharide with this activity is galactomannan. Galactomannan may be obtained from a variety of natural sources such as plants and may be made synthetically by enzymatic reactions or by chemical synthesis. Examples 1 and 2 show the effects of using galactomannans derived from two separate plant sources which have been demonstrated to be effective at reducing toxicity of therapeutic agents. In particular, Example 1 describes the use of galactomannan from a second plant species Gelditsia triacanthos and Example 2 describes the use of galactomannan obtained from the plant species Medicago falcata. 
Galactomannan is a polymer that may occur in a variety of size ranges. Moreover, the galactomannan may be derivatized or hydrolyzed to result in fragments of the native to molecule or may be reacted to provide chemically modified forms of the native molecule. Embodiments of the invention provide a galactomannan having a molecular weight in the range of 20,000-600,000 D. The galactomannan may further have a size in the range of 90-415,000 D or 40,000-200,000 D. Example 1 utilizes a galactomannan with an average molecular weight of 215,000 D while Example 2 utilizes a galactomannan with an average molecular weight of 83,000 D.
The ratio of mannose to galactose may vary according to the source of the galactomannan and the isolation procedure. In embodiments of the invention, the galactomannan may have a mannose to galactose ratio of 1.00-3.00, mannose: 0.3-1.5 galactose. The ratio of mannose to galactose may be 2.6:1.5 or 2.2:0.9 or 1.13:1 or 2.2: 1. In Example 1, the ratio of mannose to galactose is 2.2:1 and in Example 2, the selected ratio of mannose to galactose in the galactomannan is 1.13:1.
The galactomannan may be provided with the therapeutic agent in a mixture at a ratio of 0.1:1 w/w to 10:1 w/w with the therapeutic agent. In Example 1, the ratio of galactomannan to 5-FU is 1:1.9 and in Example 2 the ratio of galactomannan to adriamycin is 1:0.6. The results shown in Examples 1 and 2 are unambigious with respect to the significant reduction in toxicity observed when chemotherapeutic agents are administered in the presence of galactomannan. In Example 1, the results are dramatic. Instead of a death rate of 3/5 mice with 5-FU with the surviving mice showing substantial lack of normal weight increase, the same dose administered with galactomannan results in 0/5 mice dying. All mice survive and the surviving mice have weights equivalent to control mice (treated with saline). The surviving mice appear normal in all aspects with no sign of toxicity. In Example 2, the results clearly demonstrate the advantages of formulating a mixture of adriamycin with galactomannan. Animals treated with an LD50 dose of adriamycin according to standard toxicity tests result in a mortality of 3/5 mice. In contrast, when adriamycin is coadministered with adriamycin, the toxicity is reduced so that only 1/5 mice die. Moreover although there is some weight loss in the mice that survive, this weight loss is diminished.
In a preferred embodiment, the structure of galactomannans is a poly-xcex2-1,4-mannan backbone, with the side substituents bound via xcex11,6-glycoside linkages, for example: 
Without being bound by any particular theory, two possible mechanisms may account for the beneficial effect of galactomannan in a mixture with a toxic drug. One involves a direct physical interaction between the drug and galactomannan. For example, galactamannan may increase cancer cell membrane fluidity and permeability, as a result of galactose-specific interactions at the surface of the target cell. The polysaccharide can thus serve as an effective vehicle for delivery of the drug to the target. With respect to the treatment of cancer with chemotherapeutic agents, galactomannan may act to inhibit aggregation of tumor cells and their adhesion to normal cells, so that the cancer fails to metastasize. The toxicity of the chemotherapy drug may be reduced because the drug is inactive as long as it is bound to the polymer. Once the polymer drug conjugate enters the tumor, which galactomannan recognizes by virtue its structure and composition, galactomamman may release the anticancer drug. Another possible mode of action of galactomannan may involve its interaction with some regulatory sites in a biological system, particularly if those sites are governed by galactose-specific residues, such as galectins.
Use of the galactomannan containing formulation can have an immediate effect of increasing the responses of patients to the chemotherapy, for example, an effect is a decrease in the dosage of the agent required for effective chemotherapy, in the presence of the formulation. It will have an immediate effect by decreasing toxicity of the new drugs, and thereby improving a patient""s quality of life.
The use of galactomannan administered in a mixture with a toxic agent can be applied to a wide range of agents and is restricted to anti-tumor or anti-cancer agents. These therapeutic areas include anti-depressants, anti-inflammatory agents, gastroenterology drugs (for treating ulcers and-associated disorders), anti-psychotic drugs, anti-hyperlipidemic agents, etc. As many therapeutic agents must be administered as a chronic medicine, i.e., on a long-term basis, potential reduction in dosage and improvement in quality of life become significant factors in availability, cost of therapeutic agents, and patient compliance.
Examples of therapeutic agents with toxic side effects that may be administered with galactomannan to reduce their toxicity include the following: Anti-infectives including antibiotics, antivirals and vaccines, antineoplastics, cardiovascular drugs including antiarrythmics, antihypertensives etc., central nervous system drugs including analgesics, anorectics, anticonvulsants, anti-inflammatories and tranquilizers etc. OTICS, Opthalmics, gastrointestinal including anti-ulcer drugs, anticholinergic drugs etc. hormones, respiratory drugs including allergy medications, bronchodilators and decongestants, topical drugs and vitamins and minerals. Particular examples in the above categories are provided by way of illustration. Prilosec (AstraZeneca) described in U.S. Pat. No. 4,255,431 and Prevacid (TAP) described in U.S. Pat. No. 4,628,098; Lipitor (Pfizer) an anti-cholesterol drug described in U.S. Pat. No. 5,273,995. The antihyper-lipidemic agent, Zocor (Merck) U.S. Pat. No. 4,444,784; anti-depressants such as Prozac (Eli Lilly) described in U.S. Pat. No. 4,314,081; and Zoloft (Pfizer) described in U.S. Pat. No. 4,536,518; Paxil (SmithKline Beecham) U.S. Pat. Nos. 3,923,743 and 4,007,196; 4,721,723; antipsychotic agents such as Zyprexa (Eli Lilly) hematinic agents such as Epogen (Amgen), also known as Erythropoietin, and anti-inflammatory agents such as Celebrex (Searle). The formulations and dosages are provided in the Physicians Desk Reference.
The combination of toxic therapeutic agent together with galactomannan can be administered in any of the methods known in the art such as in a liquid formulation, tablet, suppository, gel, cream, transdermal or topical patch or aerosol. The formulation may be administered to a subject by any of the routes known in the art including by oral, mucosal, inhalation, or by parenteral administration as defined above.